Monoclonal gammopathy in extranodal marginal zone lymphoma (ENMZL) correlates with advanced disease and bone marrow involvement.

Monoclonal gammopathy is a well-recognized occurrence in splenic marginal zone lymphoma (MZL); however, its prevalence has never been reported in extranodal MZL (ENMZL). We present results of a retrospective analysis of 26 patients with newly diagnosed as well as previously treated ENMZL. Monoclonal gammopathy was detected in 7 out of 26 (27%) patients. All patients with a monoclonal gammopathy had stage IV disease, and most of them had involvement of lymph nodes and/or bone marrow (n = 6). Only 1 out of 7 patients with a monoclonal spike had stage IV disease diagnosed based on multifocal mucosal involvement. There was also a strong correlation between the involvement of bone marrow and the presence of a monoclonal spike (Fisher's exact test, P = 0.0007). Prevalence of monoclonal gammopathy is higher than previously recognized and indicates advanced disease. However, the prognostic significance of the presence of monoclonal gammopathy in this population is unknown.